I can't rep you David or I would. Some of that info I've lost or forgotten and Cheezit cleared up the foggy glass for us both!!!

 

What Cheezit says makes sense. The PCM can send a command to the HEC telling it when to turn on the "I" circuit.

What frustrates me is that the Service Manual is still wrong. In both cases, single and dual, it says the alternator "I" circuit is turned on with the key and stays on. Only in the dual alternator setup, the lower alternator is kept off until the glow plug cycle completes.

I hate giving out bad information. Especially when I thought I had completely researched it.

 

oddly the signal that hec gets is the gpcm timer thats its.
the book being wrong... dont let that bother you. thats a daily fact of my life. the shop books are often copyed and pasted from one year to the next.
waan have some fun look at the stuff for speed controll on 04 /05 my trucks, unless they finaly fixed that.

dual alternators the secondary is controlled by the pcm

 

Just to clarify I do not recomend unhooking batteries and running on alt alone. I was just trying to get the point across that I think a lot of people don't understand. A truck (any vechicle) that dies while running needs to have the alt tested as this should not happen if you have a good alt. (that's if the problem at hand pertains to the charging system). I have seen many times when a car/truck dies while driving and the owner says "well I need new batteries because it won't stay running". But yes cheezit you are all right NEVER RUN WITHOUT BATTERIES.

 

OK. So I'm a stubborn old goat. I had to find out for sure.

So I went out this morning with my clamp ammeter and hooked it to the B+ battery charge wire, went around and started the truck (it was 50 degree's outside, the truck was cold and no block heater was used), and then came around and looked at the ammeter.

Sure enough, there was no significant amperage coming from the alt. About 2-5 amps. After a minute to a minute and a half, it jumped up to 90 amps. Presumably after the glow plug cycle was over.

So now it's confirmed.

 

truly a good sport.

 

You know that is part of what makes FTE a great place. Stubborn people that won't just go with what the next guy says. Guys that will go out of there way to find out the facts. Reps to you David.
Edit.... Still have to spread the love will get you next time.

 

i really appreciate that you question what you are told, respond in a civil manner,and then go out and test the statement, even cooler is coming back to say you were previously misinformed but have learned something

 

I couldn't agree more. The information was questioned, presented factually and professionally, and TESTED for accuracy. I've asked several times (not recently) what actually controlled the alternator and now I know for sure. There are very few forums that have this level of expertise and knowledge and the willingness to test the seemingly "small" things that make a difference. I'd rep everyone involved but I'm out of clicks. Someone hit them for me please???